Determining the adhesion force between particles and rough surfaces

• The adhesion force particle–surface was carried out using the Centrifuge Technique.
• The adhesion force increases linearly with the particle diameter.
• Surface roughness plays an important role in adhesion force.
• The true area of contact is an important factor in the adhesion between particles.

Adhesion between powders and surfaces plays an important role in various industrial applications such as food and pharmaceutical industries. The Centrifugal Technique was used to measure the adhesion force distribution of several hundred particles simultaneously. The powder particles were initially forced onto the substrate surface by centrifuging them at a particular speed, and immediately after this stage, the adhesion profile was determined. The powder used was microcrystalline cellulose (ρ = 1.620 kg m− 3). The materials used as substrates were a membrane of cellulose ester 0.2 μm in porosity, brand Shleicher & Shuell Filtration Life Science, used in process monitoring particulate material and a compressed particulate (tablets) microcrystalline cellulose (MCC). A microcentrifuge that reached a maximum rotation speed of 14,000 rpm and which contained specially designed centrifuge tubes was used in the adhesion force measurements. An image analysis program (Image-Pro Plus 7.0) was used to monitor the number of particles that remained adhered on the surface of the substratum after each angular speed increase. The geometric median force of adhesion for the substrates was found to increase linearly with the preliminary applied force. The slope of each regression line indicated quantitatively the change of the median adhesion force per unit increase of the applied force. Finally, the adhesion force experimental results and the adhesion force theoretical values using the models proposed by Derjaguin, Muller and Toporov (DMT) and Johnson, Kendall and Roberts (JKR) were compared. Although the JKR Model was the closest one to the experimental results, the adhesion force theoretical values were far higher than the experimental values.

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